The present invention comprises an abrasive composition for chemical mechanical planarization (CMP), which contains abrasive particles comprising an organic resin; methods of preparing the organic resin particles; methods of tailoring the abrasive composition for selective CMP applications; and a method of preparing a semiconductor device using the abrasive composition.
CMP is a commonly used technology in semiconductor industry. The pure substrate surface and complex surface of semiconductor wafer, dielectric layer, conducting wire and barrier materials in the integrated circuits have to be polished to achieve a certain degree of planarity, which is extremely important to reach a high density of integrated circuits. In general, CMP technology consists of four major specific technologies including slurry, pad, polisher and post-cleaning device. The CMP slurry provides a chemical environment to wet and adjust the interaction between abrasive, pad and the wafer surface, and also moderates the mechanical force on the polishing surface. The slurry plays a key role in CMP process and determines the production efficiency and product quality.
The present invention relates generally to the preparation of semiconductor devices and more particularly to improved slurry compositions for the chemical-mechanical planarization (CMP) of metal (e.g., Cu) layers and barrier materials (e.g., Ta, TaN, etc.) and dielectric materials for their polishing.
A semiconductor wafer typically includes a substrate, such as a silicon wafer, on which a plurality of integrated circuits have been formed. In the manufacture of integrated circuits, wafer surface planarity and quality is of extreme importance. In order to achieve the degree of planarity required to produce ultra high density integrated circuits, CMP processes are being employed.
In general, CMP involves pressing a semiconductor wafer against a moving polishing surface that is wetted with a chemically reactive, abrasive slurry. Conventional slurries either are acidic or basic, and generally contain alumina, silica, zirconium oxide, magnesium oxide, or cerium oxide abrasive particles. The polishing surface usually is a planar pad made of a relatively soft, porous material, such as polyurethane. The pad usually is mounted on a planar platen. Continuous pad devises also are being tested. Systems devoid of a slurry where the pad contains the abrasive also are being used.
Integrated circuits are chemically and physically integrated into a substrate by patterning regions in the substrate and layers on the substrate. The layers generally are formed of various materials having either a conductive, insulating, or semiconducting nature. Also, barrier materials or barriers are used to prevent the migration of ions and adhesion promoters. In order for a device to have high yields, it is crucial to start with a flat semiconductor wafer. If the surface is not: uniform (e.g., areas of unequal elevation or surface imperfections), various problems can occur which may result in a large number of inoperable devices. Further details can be found in the following references: Luo, et al., xe2x80x9cChemical-Mechanical Polishing of Copper: A Comparative Analysis,xe2x80x9d February 13-14 CMP-MIC Conference, 1997 ISMICxe2x80x94200:197/0083; Babu, et al., xe2x80x9cSome Fundamental and Technological Aspects of Chemical-Mechanical Polishing of Copper Films: A Brief Review,xe2x80x9d Feb. 19-20, 1998 CMP-MIC Conference, 1998 IMICxe2x80x94300P98/0385; Tseng, et al., xe2x80x9cEffects of mechanical characteristics on the chemical-mechanical polishing of dielectric thin films,xe2x80x9d Thin Solid Films, 290-291 (1996) 458-463; Nanz, et al., xe2x80x9cModeling of Chemical-Mechanical Polishing: A Review,xe2x80x9d IEEE Transactions on Semiconductor Manufacturing, Vol. 8, No. 4, November 1995; Stiegerwald, et al., xe2x80x9cPattern Geometry Effects in the Chemical-Mechanical Polishing of Inlaid Copper Structures,xe2x80x9d: xe2x80x9cJ. Electrom. Soc., Vol 141, Oct. 10, 1994; Fury, xe2x80x9cEmerging developments in CMP for semiconductor planarizationxe2x80x94Part 2,xe2x80x9d Solid State Technology, 81-88, July 1995; Fury, xe2x80x9cCMP Standards: A Frustration Cure,xe2x80x9d Semiconductor International, November 1995.
Surface planarity is of paramount importance in microelectronics. With the integrated technology approaching the era of Ultra Large Scale Integration (ULSI), CMP is touted as the only viable technique to meet today""s planarity requirements. Some of the most important issues in CMP today addressed to dishing and erosion, corrosion, defects of the surface, include the control of polishing rate and selectivity among different materials on the surface. The prior art attempts to accomplish these goals as follows.
U.S. Pat. No. 4,959,113 discloses a method of polishing metal surfaces with aqueous slurries. The slurry composition comprises water, abrasives such as SiO2, Al2O3, TiO2, ZrO2, CeO2, SnO2, SiC, TiC, and a salt containing any cation of group IIA, IIIA, IVA, or IVB and any anion of chloride, bromide, iodide, nitrate, sulfate phosphate, or perchlorate. The patent also discloses a pH range of 1-6 which is adjusted with mineral acids.
U.S. Pat. No. 5,084,071 discloses the CMP slurry, which comprises abrasive particles, e.g. SiO2, CeO2, Fe2O3, SiC, Si3N4, containing less than 1%(w/w) of alumina, and a transition metal chelated salt (e.g. EDTA) as a polishing accelerator.
U.S. Pat. No. 5,114,437 discloses the CMP slurry for polishing an aluminum substrate, which contains an alumina with an average particle size of 0.2-0.5xcexc, and a polishing accelerator selected from the group consisting of chromium (III) nitrate, lanthanum nitrate, ammonium cerium (III) nitrate and neodymium nitrate.
U.S. Pat. No. 5,209,816 discloses a method for polishing Al- or Ti-containing metal layer with the CMP slurry, which contains inorganic abrasive materials, 0.1-20% by volume of H3PO4 and 1-30% by volume of H2O2.
U.S. Pat. No. 5,225,034 discloses the CMP slurry for polishing copper layer on a semiconductor wafer to produce copper wire on the wafer. The slurry comprises AgNO3, inorganic abrasive particles and an oxidant selected from H2O2, HClO, KClO, K2MnO4, or CH3COOOH.
U.S. Pat. No. 5,340,370 discloses the CMP slurry for polishing tungsten or tungsten nitride film, which comprises an oxidizing agent such as potassium ferricyanide, inorganic abrasive particles, water, and has a pH of 2-4.
U.S. Pat. No. 5,366,542 discloses a CMP slurry comprising alumina abrasive particles, chelating agent selected from the group consisting of polyaminocarboxylic acid (EDTA) and sodium or potassium salts, and may further contain boehmite or an aluminum salt.
U.S. Pat. No. 5,391,258 discloses a CMP slurry for polishing silicon, silica or silicate composite. The slurry comprises, in addition to inorganic abrasive particles, hydrogen peroxide and potassium hydrogen phthalate.
U.S. Pat. No. 5,516,346 discloses a CMP slurry for titanium film. The slurry contains potassium fluoride, inorganic abrasive particles such as silica, and pH less than 8.
U.S. Pat. No. 5,527,423 discloses the slurry for polishing a metal layer, which comprises an oxidizing agent such as iron nitrate, alumina particles containing at least 50% gamma phase, nonionic surfactants such as polyalkyl siloxanes, or polyoxyalkylene ethers.
U.S. Pat. No. 6,171,352 discloses a CMP slurry which contains, in addition to inorganic abrasive particles, an abrasion accelerator, wherein the abrasion accelerator comprises monocarboxy group- or an amino group-containing compound and optionally a nitrate salt, also a viscosity modifier such as polyacrylic acid or its copolymer.
U.S. Pat. No. 6,258,721 discloses an innovative CMP slurry using diamond particles as an abrasive material, comprising ingredients such as an oxidizing agent, chelating agent, surfactant and others.
In summary, all reported CMP slurries employ inorganic particles as abrasive materials and as such, cannot achieve the combination of an efficient polishing rate and selectivity for removing different materials from the surface. The present invention provides a novel CMP slurry that uses abrasive particles comprising an organic resin. The functionality and density of the organic particles is adjustable to control the interaction between particles and the wafer surface, that effects unique properties for CMP applications that are not available with conventional slurries containing inorganic abrasive particles.
An objective of the present invention is to provide a new CMP composition, in which the abrasive particles have tailored functionality. By varying the functionality of the particles, the interaction between the particles and the substrate surface can be controlled.
A second objective of the present invention is to decrease the hardness of abrasive particles to reduce surface scratch, which leads to wafer defect reduction and an improved post CMP cleaning step. In addition, this invention uses abrasive particles that are significantly low in density, which leads to a much more stable slurry, i.e., they do not show sedimentation of particles to the bottom of the container on standing.
The present invention, in part, is drawn to a CMP slurry comprising soft water with 0.1-20 w/w % of abrasive particles comprising an organic resin, wherein the CMP slurry is maintained at a pH between 2-12. The CMP slurry may further comprise 0.1-20 w/w % of oxidizing agent, 0.05-15 w/w % of surfactant, 0.1-15 w/w % of chelating agent, 0.001-10 w/w % of passivation agent and 0.1-20 w/w % of inorganic abrasive particles.
The present invention, in part, is drawn to a slurry (A) which can be used to selectively remove copper from a surface. This slurry comprises 0.5-20 w/w % of abrasive particles comprising an organic resin, 0-10 w/w % of an oxidizing agent, 0.1-5 w/w % of a chelating agent, 0.1-5 w/w % of surfactant, 0-1 w/w % of a passivation agent and soft water. The pH of the solution is in the range of 2-12.
The present invention, in part, is drawn to a slurry (B) which can be used to effectively remove tantalum found in barrier films and/or silica. Slurry (B) comprises 0.5-20 w/w % of the abrasive particles comprising an organic resin, 0-3 w/w % of an oxidizing agent, 0-3 w/w % of a chelating agent, 0-2 w/w % of a surfactant, 0.1-15 w/w % of inorganic abrasive particles and soft water. Slurry (B) is maintained at a pH of 2-12.
The present invention, in part, is drawn to a method for preparing the abrasive particles comprising an organic resin, said method comprising combining soft water with a substituted or unsubstituted formaldehyde, and at least one of (a) a substituted or unsubstituted melamine, (b) a substituted or unsubstituted urea, (c) a substituted or unsubstituted phenol and (d) a substituted or unsubstituted resorcinol; an optional step of adjusting the pH of the mixture to a desired value; curing the resin; and grinding the cured resin into particles having an average diameter of 0.05-5 microns.
Also, the present invention, in part, is drawn to a method of preparing a semiconductor device using the inventive abrasive slurry composition.
The present invention, in part, is drawn to abrasive particles comprising an organic resin having a hardness of less than 250 on the Rockwell Hardness scale (ASTM D785). Preferably, the hardness is from 65 to 125. The organic abrasive particles are formed of resins and can be tailored to control the interaction between the particles and the polishing substrate surface. The functionality and density of the resin particles are properties which affect this interaction between the particles and the polishing substrate surface. Thus, varying the functional groups on the resin and controlling the process for preparing the resin enables one to selectively remove individual components from a surface containing multiple components. The density of the abrasive particles is 1.2-1.6 g/cm3.
The present invention, in part, is drawn to a method of preparing the abrasive particles comprising an organic resin, said method comprising mixing soft water with a substituted or unsubstituted formaldehyde, and at least one of (a) a substituted or unsubstituted melamine, (b) a substituted or unsubstituted urea, (c) a substituted or unsubstituted phenol and (d) a substituted or unsubstituted resorcinol; optionally varying the pH of the mixture to a desired value; curing the resin; and grinding the cured resin into particles having an average diameter of 0.05-5 microns.
The term xe2x80x9csubstituted ureaxe2x80x9d as used herein includes urea molecules wherein the hydrogen atom on the amino group is substituted by an alkyl, aryl, alcohol, carbonyl or any other functional group. The degree of substitution is at least one.
The term xe2x80x9csubstituted melaminexe2x80x9d as used herein includes melamine molecules wherein the hydrogen atom on the amino group is substituted by an alkyl, aryl, alcohol, carbonyl or any other functional group. The degree of substitution is at least one.
The terms xe2x80x9csubstituted phenolxe2x80x9d and xe2x80x9csubstituted resorcinolxe2x80x9d as used herein include phenol and resorcinol molecules, respectively, wherein the hydrogen atom on the phenyl group is substituted by an alkyl, aryl, alcohol, carbonyl or any other functional group. The degree of substitution is at least one.
Thus, the xe2x80x9corganic abrasive particlesxe2x80x9d are composed of a formaldehyde-based resin or combination of formaldehyde-based resins such as melamine formaldehyde, substituted melamine formaldehyde, urea formaldehyde, substituted urea formaldehyde, phenol formaldehyde, substituted phenol formaldehyde, resorcinol formaldehyde, and substituted resorcinol formaldehyde. The formaldehyde-based resin(s) can be mixed with other thermoplastic polymer(s) and/or rubber(s).
The relative ratio of the formaldehyde monomers to the other monomers has an effect on the selectivity of the slurry composition.
The water used in the process of forming the formaldehyde-based resin and in the abrasive slurries is preferably xe2x80x9csoftxe2x80x9d. The term xe2x80x9csoftxe2x80x9d as used herein means that the water has less than 500 ppm heavy metal impurities. Preferably, the soft water has less than 50 ppm heavy metal impurities. Salts and other impurities that do not significantly reduce the yield of the formaldehyde resins or significantly effect the polishing process of the abrasive slurry, do not necessarily need to be removed from the water prior to the polymer synthesis step.